Monday, June 22, 2015

99 wins, one fail for DEQ

Discovering that I could easily program one passband of an electronic crossover for a multi-amplified system into a Behringer DEQ 2496, I have been planning to buy 3 more units, or something like that. It turns out these are (mostly) the most versatile units I know of, nicely made, and cheap. The have AES digital I/O, which is how I use them (forget the analog bits, those I want to avoid as much as possible, though I still am, mostly, and with little technical loss, they are objectively good enough when not used above 4V output not to have any proven audible flaws, but of course they are not built with audiophile design or jewelry). And optical, so you can have two parallel outs (optical and digital…another fact I take advantage of). Just the most useful little tool for me now, though I could dream of something similar and fully programmable, pop up a programming interface when you plug it into your compeer via USB, …

The DCX 2496 crossovers, which I still use except for the panel passband, don't have digital output. If they just had that, they would be invaluable…though I don't really like the SRC they use, they convert everything to 96kHz. The DEQ's don't do SRC, they pass the input to the output without changing sampling rate. I prefer that, so I'd prefer that to having a modified DCX with digital I/O (I expect that would cost about as much as 3 DEQ's too). The DEQ has a bigger screen, it has meters and spectrum analyzer…it's just cooler to have one of these for each passband than a DCX, except of course for the added cost and complexity. But if you need it, you need it. (Wait. Why do I need it?)

Except, except one thing I wasn't expecting at all. I guess it doesn't actually derail my plan, but it is a big disappointment, and it also in-general-now (but not wrt my Big Test, in the Long Run after I Work This Out) ruins my plan to use midi-programming of a DEQ to implement level changing for ABX testing.

The Behringer DEQ 2496 doesn't have separate level controls for each channel. It's mind boggling that a thing with so many features lacks this one basic thing. You can set overall "makeup gain" to 0.1 dB in the Utilities panel, which is fine though it seems peculiar to relegate so critical a thing to the back door, but there is no separate Right and Left or whatever, anywhere.

What the Behringer does have is a "Rotation" control, that allows you to set "Rotation" (something like balance) to 1 degree. But that is not close to being good enough, has a non-linear relationship with the dB difference, and inconveniently affects both channels at once (in the opposite direction). Even with a mere 0.3dB difference between the channels of my Krell, 1 degree of rotation overshot the mark. I was easily able to dial in the correction on my Tact RCS 2.0, which had been set to 0/0. (I had been worried that previous adjustment had been the cause of the 0.3dB difference.)

So this won't work for fine tuning levels for ABX testing. It's basically good enough for crossovers in my system. I can adjust the all-critical wide range middle speaker using the Tact, the subs can be adjusted with their own controls, and I have no idea how many dB wrong the current super tweeter balance is, and they are effectively inaudible at the listening position. (If I do need to rebalance the super tweeters because they are noticeably different, as they look, quite possible the rotation control will be sufficient--that's about audible difference generally--ABX testing is actually to a much higher standard.)

So, for ABX testing, I'll have to use some other level adjustment-in-general-and-now, AND I have the sad knowledge that the Aragon has quite a bit less output than the Krell, not the reverse, so the Krell would need to be attenuated, and that Won't Do, so any arrangement will have to be temporary or something.

However for general use, the Midi control with 0.1dB control regarding level (if not L-R) will do fine, and that may do (with some adjustment/correction) even for a permanent Krell/Aragon installation. I'll get the L-R balance of both perfected through other means, then changing the overall level is all that's needed.

Other things should have their balanced fixed first also. So the Only thing we absolutely need is level (real L/R control would have been nice, somethings won't be testable, even right now they aren't, and I'm not going to put permanent attenuators of any stripe on the line to the Krell, I just won't.

The Krell has been sounding marvelous, btw. Over the weekend, listening to FM mainly. I was even drawn to Opera for awhile. I had to setback the thermostat first 2 degrees and finally 3, taking back the 3rd when I put the Krell in standby. Standby ended on Sunday night, though I've had the Krell on tonight for testing as described above.

I'm OK with raising the thermostat if I can have my Krell.

Apologies to those who say everything must be scientific. At home, in my closet of a living room, I practice magic. Magic requires suspension of disbelief. The magician makes big sacrifices, lifts the Krell up onto the altar, and everything has a purpose…